The research has the following objectives: 1. To develop a family-oriented model of diagnosis and outreach intevention for failure-to-thrive infants and their families. 2. To assess the effectiveness of this treatment model through objective measures of the physical and psychological progress of these infants and their families. 3. To identify the features of parent-child interaction which best predict physical and psychological progress. Failure-to-thrive infants and their family will receive a comprehensive care pattern organized in two separate phases, hospitalization and aftercare, and managed by an interdisciplinary team. This team approach will facilitate family involvement in the diagnostic and treatment process and coordination between medical and psychosocial services. Following hospitalization, the study group will receive a family-oriented mental health intervention focused on the remediation dysfunctional family interactions and reinforcement of adaptive features of parent-infant relationships. The effectiveness of treatment will be evaluated through detailed observations of parent-child interaction and systematic follow-up of infants' physical growth, intellectual, social, and family functioning.